The purpose of this study is to characterize the pharmacokinetics (PK) of LY03004 following an escalating single intramuscular injection at 12.5, 25, 37.5, or 50 mg; and to evaluate the safety and tolerability and preliminary efficacy of LY03004 following intramuscular injection.

Inclusion Criteria:

1. Male or female patients aged 18 to 65 years old;
2. Patients must have a DSM-IV diagnosis of schizophrenia or schizoaffective disorder based on the Mini-International Neuropsychiatric Interview (MINI);
3. Patients must be clinically stable on antipsychotic medications other than risperidone or paliperidone or clozapine for at least 4 weeks prior to screening, based on clinical assessments and a Positive and Negative Syndrome Scale (PANSS) total score less than or equal to 70 at screening visit;
4. Patients with a Body Mass Index in range of 18.0 to 35.0;
5. Patients with an Informed consent form signed by the patient or legally acceptable representative

Exclusion Criteria:

1. Patients with a mental disorders other than schizophrenia or schizoaffective disorder, according to the DSM-IV;
2. Patients who received oral risperidone or paliperidone or clozapine within 14 days prior to screening, or Risperdal Consta within 100 days prior to screening or paliperidone palmitate within 10 months prior to screening;
3. Patients with neuroleptic malignant syndrome or physical fatigue associated with dehydration or malnutrition;
4. Patients who pose a significant risk of a suicide attempt based on history, investigator's judgment or have answered "yes" on the questions 4 or 5 for current or past 30 days on the screening form of the Columbia Suicide Severity Rating Scale (C-SSRS).
5. Patients with a history of sensitivity to akathisia and other EPS, especially with previous use of risperidone or paliperidone.
6. Patients with uncontrolled diabetes mellitus as indicated by a HbA1c level greater than or equal to 7%;
7. Patients with a history of or currently having epilepsy or convulsion disorders;
8. Patients who have had electroconvulsive therapy within the past 2 months prior to screening;
9. Patients who used medication known to be an inducer or inhibitor for CYP 2D6 less than 2 weeks prior to screening;
10. Patients with a history of allergic reaction to risperidone or to the excipients of LY03004;
11. Patients who have met DSM-IV-TR criteria for substance abuse or dependence with the exception of caffeine or nicotine in the past 6 months prior to screening
12. Patients with a history of clinically relevant cardiac arrhythmia's, cardiovascular disease, thyrotoxicosis, parkinsonism, or hemorrhagic diathesis;
13. Patients who are currently taking medications with primarily CNS activities such as antidepressants, mood stabilizers or anticonvulsants;
14. Patients who have participated in a clinical trial of another investigational drug within 30 days prior to screening;
15. Female patients who are pregnant or are breastfeeding or are of childbearing potential without adequate contraception.
16. Patients who have any clinically relevant hepatic, renal and cardiac dysfunction, or other medical condition or laboratory abnormality, which in the judgment of the investigator would interfere with the subject's ability to participate in the study